Adam Nathan's Windows Presenation Foundation Unleashed book, published by SAMS. Adam's book seems to be the main go to book for most .NET developers trying to learn WPF programming. I think the main thing that sets Adam's book apart from just about every programming book that has hit the shelves at this point is it is Full Color. Yes just like the Brady Bunch we now have a programming book published in four colors, which is quite an accomplishment.
The color permeates throughout the book in screen shots, source code and various comment call outs that extra value to the topics. This is very helpful for someone trying to grok what is going on with WPF, which once you get into the book you will quickly realize this is not your father's user interface markup. WPF is difficult to do effectively, which is why the Windows Presentation Foundation Unleashed book by Adam Nathan is a very important introduction to this new paradigm.
Adam covers all the basic concepts in WPF and takes things a little beyond just introduction topics. He covers Styles, Templates Skins and Themes and the ever important Data Binding concepts. I am still struggling to do Data Binding the way I want to, which is at run-time and not declaratively. If there was any disappointment with the Unleashed book it was the lack of explanation of what I would deem business quality data binding information. But that seems to be the case with most WPF examples up to this point.
The book is about 600 pages of quality WPF learning. I was able to read through the book on a flight to MIX back in April, seriously I did. I plan on using it as a reference as I now have some cycles to start doing WPF and Silverlight development this Fall.